Process for straightening metallic articles



June 18, 1963 WALTON ETAL 3,094,160

PROCESS FOR STRAIGHTENING METALLIC ARTICLES Filed Jan. 22, 1960 2 Sheets-Sheet 1 c l I l9 I8 I l l a; an I) i I 1 I L. L T J L, W

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June 18, 1963 E. WALTON ETAL 3,094,160

PROCESS FOR STRAIGHTENING METALLIC ARTICLES Filed Jan. 22, 1960 2 Sheets-Sheet 2 United States Patent Q 3,094,160 PROCESS FOR STRAIGHTENING METALLIC ARTICLES Eric Walton, Halton, Leeds, Michael Hilton Joseph Lord,

Leeds, and Peter Austin, Churwell, Leeds, England, assignors to Daniel Doncaster & Sons Limited, Sheflield, England Filed Jan. 22, 1960, Ser. No. 4,044 17 Claims. (Cl. 153-32) The present invention relates to a process for straightening metallic articles by means of a hot die press, and to apparatus for carrying out this process.

In the manufacture of metallic articles, for example of precision forged compressor blades, it is often necessary to correct distortions, such as. twist distortions or bow distortions, brought about during their manufacture, for example, immediately after hot or cold working, or during heat treatment.

A process for performing this operation has been pro posed, comprising rigidly clamping the article in a cold jig and heating the jig and its contents to a temperature suitable for straightening the article, and then allowing the article, still firmly clamped in its jig, to cool. This process has the drawback that it requires a comparatively long time, of the order of a few hours, for each operation cycle.

It is an object of the present invention to overcome this drawback.

According to. one aspect .of the present invention a process for straightening a metallic article which has been brought to approximately its desired shape comprises heating the article to a predetermined temperature appropriate to the material of which the article is made, hereinafter termed the straightening temperature, subjecting the article to pressure for only a small fraction of the usual straightening time in a die kept at substantially the same predetermined temperature, thereafter removing the article fromthe die, and allowing the articleto cool.

By straightening is meant that the article which has been straightened remains in its straight position after any external forces acting on it to produce said straightening' have been released, and by a small fraction of the usual straightening time is meant an interval of the order of a few minutes as compared with a period of the order of an hour or more, as in the case of the straightening process already proposed and described hereinabove.

The article may 'be preh eated toa temperature higher than that of thedie before being transferred to the die, while the temperature range for carrying out the process properties of the material to be treated. Aluminium alloys, for example, are conveniently treated at a temperature of the order of 100 C., while stainless steels require temperatures of the order of l-000 C. The upper limit of the temperature range is. at present limited only by the availability of suitable die materials. The temperature chosen will depend, among other things, on the desired mechanical properties of the straightened article, and the effect on previous or subsequent heat treatment.

The article may remain in the die for any suitable and effective length of time and intensity of pressure, according to its bulk and shape, and according to the nature of the material, of which it is made, preferably between half a minute to ten minutes.

The process may also be carried out in a controlled atmosphere, such as an argon atmosphere or in a vacuum. Such a process is especially recommended for temperatures in the region above 800 C. to prevent scaling of precision forgings, for example, in the case of titanium alloys or alloys having a high nickel content.

According to a further aspect of the present invention,

apparatus for carrying out the process comprises a furnace, an electrically heated die, a press for subjecting the die to a predetermined pressure, and control means simultaneously controlling the temperature of the furnace and of the die and the time during which'the die is subjected to said pressure.

may be between C. and 1200' C., according to the The control means may further simultaneously record the quantities being controlled.

Where the materials require it, the apparatus may be so arranged as to operate in a controlled atmosphere or in a vacuum.

One form of apparatus according to the invention will now be particularly described by way of example with reference to the accompanying drawings, in which:

FIGURE 1 is a front elevation of a furnace and straight ening press;

FIGURE 2 is a fragmentary side elevation, partly in sectional elevation of an electrically heated tool holder for use With the straightening press of FIGURE 1;

FIGURE 3 is a schematic circuit diagram of the associated control means for the press and furnace shown in FIGURES 1 and 2.

Referring to FIGURE 1 of the drawings, apparatus for straightening metallic articles, for example, heat resistant stainless steel compressor blades, comprises an electric furnace 11 mounted in a convenient position for the operator next to a pneumatic variable load press 12 arranged to be controlled by a process timer 13 which determines the length of time pressure is applied. A combined recorder and controller for automatically supervising the operation of the press and furnace is indicated at 14, while the press comprises an air cylinder 15 and columns 16 capable of drawing a cross head 17 downwardly to compress press platens 18 (FIGURE 2).

The press platens 18 are arranged to cary tool holders 19. The tool holders 19 are each provided with a tool cavity 20 and with tool locating posts 21, while an electric heating element 22 is accommodated in an extension of the tool cavity 20 of each tool holder 19. A thermocouple 23 is provided to measure the temperature obtaining in the tool holder 19 and dies 20a, and automatically energizes or switches off the electric heating elements 22 as required.

Referring to FIGURE 3 of the drawings, a source of alternating current supplies the entire control system shown schematically in the figure. The supply to the system is controlled by a switch fuse 24 and a three pin plug. and socket 25 in the usual manner, and branches into several paths, which are themselves interrelated by the circuit components they contain.

A first path suppliesv the combined recorder and controller 14 by way of a switch 26, While hold-in relays 27 and 28 control cont-actor 29 and 32 for the tool holders 19 and the furnace 11 respectively. The contactor 29 switches the heating elements 22 (FIGURE 2) of the tool holders 19 on or off as directed by the controller 14, the supply being drawn from the main supply by way of a transformer 30 and fuses 31. The temperature of the heated dies and toolholders 19 is monitored by a thermocouple 23 as already described hereinabove, the output of the thermocouple being connected to the appropriate point of the controller 14.

Similarly the temperature of the furnace 11 is also monitored by a thermocouple 230, the entire furnace being connected to the supply by way of a four pin plug and socket 34, and the points of the contactor 32. The furnace door operates a furnace door switch 33 so that the contactor 32 can only be operated when the furnace door is closed. The furnace is switched on or off as directed by the controller 14 acting through the relay 28 and contactor 32.

The process timer 13 and its ancillary components are connected in parallel with the controller 14. Push buttons 36 normally closed, 37 normally open, and 38 normally closed, and a contactor 35 control the operation of an air valve 39 for lowering or raising the pneumatic press 12, While a process lamp 40 is arranged to give warning to the operator. A further contactor 41, points 42 and 43, and a safety lamp are connected in parallel with the timer 13 in the usual way.

Where the material constituting the metallic article to be treated so requires, the apparatus may be arranged to operate in a controlled atmosphere, for example, one of argon, or in a vacuum.

Some applications of the process using the apparatus as hereinabove described are particularly described in the following examples, in which all percentages given are by weight.

Example 1 Precision forged titanium compressor blades made of an alloy comprising 2% aluminium, 2% manganese, 0.1% carbon, 0.2% iron, 0.011% hydrogen, the remainder being titanium, were heated in the furnace to 670 C., and were then held in the dies, also at 670 C., for a period of three minutes. The blades were subsequently removed from the dies and air cooled. It was found that no subsequent distortion took place in the straightened blades.

Example 2 Precision forged titanium compressor blades made of the alloy commonly available under the designation ICI alloy T1 679, were preheated to 900 C. for twenty minutes in the furnace, and then held in the dies, also at 900 C., for five minutes. The blades were then removed and air cooled. Here again no subsequent distortion was found to take place.

Example 3 Precision forged compressor blades made of heat resistant stainless steel having a composition of 0.4% carbon, 2% silicon, 0.5% manganese, 8% nickel, 20% chromium, 3% tungsten, the remainder being iron, were preheated in the furnace to 900 C. for twenty minutes. They were then held in the dies, also at 900 C. for ten minutes, and were then removed and air cooled. No subsequent distortion was found to have taken place.

It will be seen that by the use of the process and apparatus according to the invention a great saving in the time required for straightening metallic components is achieved.

We claim:

1. A process for straightening a metallic article which has been brought to its finished desired shape and has subsequently undergone distortion due to undesired internal stresses, comprising heating the article to a predetermined temperature appropriate to the material of which the article is made, placing the article in a die 4 kept at substantially the same predetermined temperature as said object, maintaining said article in said die under pressure at said predetermined temperature for a predetermined period of time, and thereafter removing the article from the die and allowing the article to cool.

2. A process as claimed in claim 1, wherein the metallic article is first preheated to a temperature higher than that of said die.

3. A process as claimed in claim 1, wherein the metallic article is made of a titanium alloy.

4. A process as claimed in claim 1, wherein the metallic article is made of a heat resistant stainless steel.

5. A process as claimed in claim 1, wherein the metallic article is made of an aluminum alloy.

6. A process as claimed in claim 1, wherein said predetermined temperature is between C. and 1200 C.

7. A process as claimed in claim 6, wherein said predetermined temperature is between 700 C. and 1200 C.

8. A process as claimed in claim 1, wherein said metallic article is kept in said die for a period of time between half a minute and ten minutes.

9. A process as claimed in claim 1, wherein said process is carried out in a controlled atmosphere.

10. A process as claimed in claim 9, wherein said controlled atmosphere is one of argon.

11. A process as claimed in claim 1, wherein said process is carried out in a vacuum.

12. A process for straightening a metallic object comprising heating the object, maintaining the temperature of the heated object while under pressure in a die at a fixed predetermined temperature for a fixed predetermined period of time, and then removing the object from the die and allowing it to cool.

13. A process as claimed in claim 12 wherein the metallic object is preheated before being placed in the die.

14. A process as claimed in claim 12 wherein said fixed predetermined temperature is between 100 C. and 1200 C.

15. A process as claimed in claim 14 wherein said fixed predetermined temperature is between 700 C. and 1200 C.

16. A process as claimed in claim 15 wherein said fixed predetermined period of time is substantially between one half a minute and ten minutes.

17. A process as claimed in claim 12 wherein said metallic object is maintained in an inert atmosphere.

References Cited in the file of this patent UNITED STATES PATENTS 1,429,138 Harry Sept. 12, 1922 1,801,110 Ruder Apr. 14, 1931 2,419,864 Westin Apr. 29, 1947 2,737,224 Jones Mar. 6, 1956 2,814,101 Prongh et al. Nov. 26, 1957 2,893,459 Kosek July 7, 1959 

1. A PROCESS FOR STRAIGHTENING A METALLIC ARTICLE WHICH HAS BEEN BROUGHT TO ITS FINISHED DESIRED SHAPE AND HAS SUBSEQUENTLY UNDERGONE DISTORTION DUE TO UNDESIRED INTERNAL STRESSES, COMPRISING HEATING THE ARTICLE TO A PREDETERMINED TEMPERATURE APPROPRIATE TO THE MATERIAL OF WHICH THE ARTICLE IS MADE, PLACING THE ARTICLE IN A DIE KEPT AT SUBSTANTIALLY THE SAME PREDETERMINED TEMPERATURE AS SAID OBJECT, MAINTAINING SAID ARTICLE IN SAID DIE UNDER PRESSURE AT SAID PREDETERMINED TEMPERATURE FOR A PREDETERMINED PERIOD OF TIME, AND THEREAFTER REMOVING THE ARTICLE FROM THE DIE AND ALLOWING THE ARTICLE TO COOL. 